1. Field of the Invention
The present invention relates to a door opening/closing mechanism having a guide part to guide an opening and closing movement of the door supported by a support part.
2. Related Art
Typical conventional door opening/closing mechanisms are of the hinge type, sliding type, slide rail type, folding door type or swing arm type, which will be shown in the below explanation. Incidentally, the below explanation exemplifies a door that is provided in a cab of a construction machine.
FIGS. 1A and 1B are plan views of a conventional hinge-type door opening/closing mechanism, while FIGS. 1C and 1D are front views thereof. FIGS. 1A and 1C show a door 2a in a closed state and FIGS. 1B and 1D show the door 2a in an opened state. This scheme has hinges 3 as a support part to support the door 2a on a main body 1, as shown in FIGS. 1C and 1D. The door 2a opens and closes along an arcuate track 5 around an axis 4 of the hinge 3.
FIGS. 2A and 2B are plan views of a conventional sliding-type door opening/closing mechanism, while FIGS. 2C and 2D are front views thereof. FIGS. 2A and 2C show a door 2b in a closed state and FIGS. 2B and 2D show the door 2b in an opened state. The sliding-type door opening/closing mechanism employs a rail or the like in the guide part to guide the opening and closing movement of the door 2b. Thus, the door 2b is allowed to move horizontally, for opening/closing, on the same plane of a side surface of the main body 1.
FIGS. 3A–3C are plan views of a conventional, general slide-rail type door opening/closing mechanism, while FIGS. 3D and 3E are front views thereof. FIGS. 3B and 3D show a door 2c in a closed state and FIGS. 3C and 3E show the door 2c in an opened state. The slide-rail type door opening/closing mechanism uses in its guide part a guide 7 curved at one end, to be seen through a top window shown in FIG. 3A, to guide the upper part of the door 2c, a rail 8 shown in FIGS. 3B–3E, and a roller 9 attached on the door 2c. As shown in FIG. 3B–3E, the door 2c is allowed to open and close along the rail 8 while being kept nearly parallel with an outer side surface of the main body 1. The door 2c, in the closed position, comes inward as shown in FIG. 3B because of the curve provided at one end of the guide 7.
FIGS. 4A and 4B are plan views of a conventional, general folding-type door opening/closing mechanism, while FIGS. 4C and 4D are front views thereof. FIGS. 4A and 4C show a door 2d in a closed state while FIGS. 4B and 4D show the door 2d in an opened state. The folding-type door opening/closing mechanism is structured with the door 2d divided in a plurality of vertical parts as shown in FIGS. 4A–4D. The divisional door parts in plurality are connected to one another by hinges 3 or the like, to connect one end thereof to the main body 1 by hinges 3. By folding the door parts as shown in FIGS. 4B and 4D, the opening and closing operation is performed.
FIGS. 5A and 5B are plan views of a conventional, general swing-arm type door opening/closing mechanism, while FIGS. 5C and 5D are front views thereof showing the arm 10 seen through therein. FIGS. 5A and 5C show a door 2e in a closed state and FIGS. 5B and 5D show the door 2e in an opened state. The swing-arm type door opening/closing mechanism is structured with an arm 10 supporting the door 2e on the main body 1 and a guide rod 11 having nearly the same length as that of the arm 10. As shown in FIGS. 5A and 5B, in this scheme, the arm 10 and the guide rod 11 are allowed to simultaneously rotate around axes 10a, 11a between the respective side and the main body 1. Due to this, the door 2e opens and closes along arcuate tracks 12 around the axes 10a, 11a while being kept nearly in parallel with the side surface of the main body 1.
However, the conventional door opening/closing mechanisms involve the following problems.
The hinge-type door opening/closing mechanism shown in FIGS. 1A–1D is frequently used in buildings, vehicles and the like. However, it requires a large space such as the inside space of the arcuate track 5 during opening and closing, shown in FIGS. 1A and 1B. This increases the amount of swing of the door 2a out of the side surface of the main body 1, and makes the opening/closing operation difficult within a limited space. Also, because the door 2a rotates vigorously if flapped by the wind in its opening/closing operation, a person who holds a grip attached on the door 2a may be swung together with the door 2a. In a construction machine, because the entrance/exit is located high and the step is possibly narrow, there is an increased danger that the person might fall. Meanwhile, when the door 2a is opened, the end of the door 2a projects outward as shown in FIG. 1B. Consequently, when this door mechanism is used in the cab of a construction machine, a door of a machine room which is located at the rear of the cab is not allowed to open by the projected part. Also, because the axis 4 of the hinge 3 projects from the side surface of the main body 1, a loss is caused in respect of unit arrangement in the case that the machine overall width upon transporting is limited as in construction machinery. Furthermore, there is a need to arrange the axes 4 of the upper and lower hinges 3 on one straight line. Due to this, a portion of the door to which the hinges 3 are attached must be in a straight-line form, which imposes a restriction in designing the form of the door 2a. 
The sliding-type door opening/closing mechanism shown in FIGS. 2A–2D is also frequently used in buildings, vehicles and the like. This scheme does not require a large space in opening and closing the door 2b. However, as shown in FIGS. 2A and 2B, the rail 6 which guides the movement of the door 2b is always exposed outside so that the rail 6 is readily rusted out and corroded due to rainwater, sea breezes or the like, and adhere with sand, dust or the like, making it impossible to obtain a smooth operation. Consequently, an increased force may be required for opening and closing the door 2b, which possibly leads to trouble. Also, it can be considered that the door 2b can fall off due to a worn-out guide surface in the rail 6. Also, a space where the door 2b moves parallel is needed in the inside of the main body 1. This reduces the efficient space in the inside of the main body 1 corresponding to a door container. Besides, air-tightness is difficult to secure because of the opening/closing mechanism structure for the door 2b to merely slide relative to the main body 1.
The slide-rail type door opening/closing mechanism shown in FIGS. 3A–3E does not require a large space in opening and closing the door 2c. Also, because the door 2c closes inwardly due to guiding by the guide 7, air-tightness is readily secured. However, because the rail 8 is always exposed outside similarly to the sliding type door as shown in FIGS. 3B and 3C, the rail 8 is liable to rust and corrode due to rainwater, sea breezes or the like, and adhere with sand, dust or the like, making it impossible to obtain a smooth operation. Consequently, an increased force may be required in opening and closing the door 2c or deformation or damage in parts may occur due to caught foreign matters, which possibly leads to trouble. Also, because there are many special formed parts, such as the guide 7, the rail 8 and the roller 9, used in the guide part, the attaching part is complicated in the form and parts cost increases. Also, the use of the rail 8 and the roller 9 in guiding the door 2c increases the resistance due to sliding friction, requiring an increased force in opening and closing operations. Meanwhile, it can be considered that the door 2c can fall off due to wear in the guide surface. Also, the rail 8 for guiding the door 2c is centrally positioned in the side surface of the main body 1, injuring the beauty of exterior design. Furthermore, as shown in FIG. 3A, particularly when the door mechanism of this type is applied to a vehicular cab or the like, the curved guide 7 possibly blocks the upper visibility of the top window.
In the folding type door opening/closing mechanism shown in FIGS. 4A–4D, the angle between the door 2d and the main body 1 side surface is nearly 90 degrees when the door 2d is fully opened. Whether the door 2d is folded inward or outward of the cab, the protrusive amount of the door 2d is great, requiring a large opening/closing space. Thus, for a limited space, there are many disadvantages in respect of unit arrangement or entrance/exit space. Meanwhile, for saving space when the door 2d is folded, there is a need to make the door 2d flat with a rectangular outer shape and, as a result, the freedom in exterior design is restricted. As can be seen from FIG. 4C, window frames occupy a large area as the door 2d is divided. This turns out a smaller space for windows. When this type of door mechanism is applied to a vehicle cab, the dead angle increases.
The swing-arm door opening/closing mechanism shown in FIGS. 5A–5D moves while being kept nearly parallel with the side surface of the main body 1. During opening and closing, the door 2e projects outward from the side surface of the main body 1 by an amount corresponding to the length of the arm 10 or guide rod 11. Consequently, in case a person stands in front of the door 2e, the person is hit by the door 2e. Also, it is not convenient in a narrow place such as nearby a wall where there is only a limited space outside the door 2e. Also, the arm 10 is largely curved in order to prevent the arm 10 from contacting the main body 1 when the door 2e is fully opened. Consequently, when the door 2e is closed, the effective space inside the door 2e is limited by the curved arm 10 as shown in FIG. 5A, causing a great loss with respect to interior unit arrangement. Also, the arm 10 is attached generally at the center of the door 2e while the guide rod 11 is attached at the front or rear end of the door 2e. However, because the other end of the door 2e is not restricted, the door 2 chatters when the door 2e is opened and closed.